Wikipedia:Reference desk/Archives/Science/2009 November 7

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November 7

Name that chemical

When I started working here in the semi-conductor manufacturing business, I was told of a chemical that wouldn't harm skin if the skin came in contact with the chemical. What would happen though, is that the chemical would soak into the tissue and settle in the person's bones and that's where it would cause considerable pain. I've looked it up before but it's been years. Can anyone remind me what this chemical is? Dismas|^(talk) 05:58, 7 November 2009 (UTC)

Hydrofluoric acid. Truthforitsownsake (talk) 06:19, 7 November 2009 (UTC)

Sounds a lot like benzene. Benzene causes bone marrow damage, can be absorbed through the skin,[1] and is used in the semiconductor industry.[2] Red Act (talk) 06:31, 7 November 2009 (UTC)

Thanks for the info about benzene but hydrofluoric was the one I was thinking of. Thanks, Dismas|^(talk) 11:35, 7 November 2009 (UTC)

is it possible I received permament eye damage from briefly handling apple's laser mouse at an Apple store.

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

This removal is discussed here. -- Scray (talk) 14:18, 8 November 2009 (UTC)

Taxonomy

Could please someone provide the taxonomic name of these flowers? Thanks in advance! -- Etienne (talk) 13:55, 7 November 2009 (UTC)

Wow, a botany question that I can actually answer -- the first time ever! The first one looks like common madia, better known as tarweed. The picture in the common madia article doesn't look the same, but I think I'm right, it's a pretty common flower here in the Bay Area. (If not common madia, then some other type of madia, there are a ton of them.) I don't know what the second one is. Looie496 (talk) 17:31, 7 November 2009 (UTC)

The second one is cosmos_bipinnatus, I also have some doubts that the first is common madia. Richard Avery (talk) 18:44, 7 November 2009 (UTC)

Thank you! -- Etienne (talk) 18:29, 10 November 2009 (UTC)

Is lightning a spark?

Arguing definition is fun! Vimescarrot (talk) 15:59, 7 November 2009 (UTC)

Slow-motion footage of lightning (Please don't embed 2MB animated GIFs to the Ref Desk... some of us don't have the fastest connections and it screws up the whole page. Changed from embedded image to link... --Mr.98 (talk) 18:13, 7 November 2009 (UTC).)

As fun as it may be, the ref desk is not a chat room or a place for debates. Though I don't see what there is to argue about: see Electrostatic_discharge#Sparks. —Akrabbim^talk 16:26, 7 November 2009 (UTC)

Yes. Both "lightning" and "sparks" are essentially electrostatic discharges. The only significant difference is perhaps that of intensity: lightning is actually an electric arc, while a "spark" technically need not "plasma-ize" the air it passes through (apparently, at least according to the intro of the Corona discharge article...).

In any case, according to Electrostatic discharge#Sparks:"Perhaps the best known example of a natural spark is a lightning strike."

Wikiscient 16:36, 7 November 2009 (UTC)

I saw the discharge article, but wanted to check with you to make sure the article was right. Sorry, I didn't mean to imply I wanted to spark (ha!) an argument with you; I'm arguing with someone else. Thanks for the responses. Vimescarrot (talk) 16:43, 7 November 2009 (UTC)

Well in that case, argue your heart out! —Akrabbim^talk 16:49, 7 November 2009 (UTC)

I think the best way to look at it is: lightning is a "spark," but not all sparks are lightning... ;) Wikiscient 16:51, 7 November 2009 (UTC)

That animated GIF of the lightning is fake, right? Tempshill (talk) 19:42, 7 November 2009 (UTC)

I think it's real. And how dare people not wait for me to get to this question. SpinningSpark 21:47, 7 November 2009 (UTC)

I would love to know the detail of how it was filmed. How fast a camera is being used there? APL (talk) 00:03, 8 November 2009 (UTC)

Don't know about that gif, but Ultraslo uses 3000 FPS. That's not the only slow-motion lightning video on Youtube, and many put their FPS in their description. Vimescarrot (talk) 00:31, 8 November 2009 (UTC)

We used cameras (and camera-like devices) with frame rates as high as 15,000 frames per second, to record lightning and lightning-related transient luminous events. Often, these high-data-rate optical devices needed electronic triggers to activate them and initiate a burst-mode recording. Nimur (talk) 03:57, 8 November 2009 (UTC)

Ben Franklin's and others' research in the 1750's indicates an affirmative answer. Edison (talk) 04:04, 8 November 2009 (UTC)

Torch lights

Will shining 2 torch lights into a particular area make the resulting light brighter? Clover345 (talk) 17:37, 7 November 2009 (UTC)

Yes. It won't, however, make it look twice as bright. The human eye perceives brightness logarithmicly, that means doubling the actual brightness (by shining twice as much light at it) will make it look a fixed amount brighter (ie. it will add something to the brightness rather than multiply the brightness by 2). See Weber–Fechner law#The case of vision. --Tango (talk) 18:05, 7 November 2009 (UTC)

Also, don't forget interference (as shown by Young's slit experiment. Shutting off a light in the room will lower the overall amount of light in the room, but the areas that were previously in the interference path of multiple light sources might actually get brighter. John Riemann Soong (talk) 23:11, 7 November 2009 (UTC)

That's a really terrible answer! Do you have any idea how narrow those interference regions are? No! Of course you don't or you'd never have said that. You'd need a microscope to see them. Where are these "slits" that are necessary for the effect to work? Do you realize that flashlight bulbs or flashlight LED's are not point sources - and they aren't monochromatic and they aren't coherent? Have you ever heard of diffuse scattering? A little knowledge is a dangerous thing! It is absolutely not the case that turning on a second flashlight will make any measurable part of the room measurably darker. Your answer is confusing and flat out incorrect. Tango had it right - the end. SteveBaker (talk) 23:48, 7 November 2009 (UTC)

Well deserved thanks to our bright knight for saving this answer! DRosenbach ^{(Talk | Contribs)} 14:59, 8 November 2009 (UTC)

Why do my glasses have a shadow?

My eyeglasses are transparent and yet when it's very bright and light is angled properly, the lenses have a shadow. Why is that? 69.77.250.210 (talk) 19:13, 7 November 2009 (UTC)

Lenses work by difraction, bending and redirecting the incident light. There is still the same amount of light hitting the lens, but because it is not going "straight through", the area straight through is not as brightly illuminated as the surrounding area that is directly illuminated. DMacks (talk) 19:26, 7 November 2009 (UTC)

It could also be because they aren't perfectly transparent. The diffraction (note spelling!) can cause some bright spots which are brighter than the surrounding area, this means the average brightness is about the same. --Tango (talk) 19:29, 7 November 2009 (UTC)

Thank goodness redirects help when my riting is not good. DMacks (talk) 19:32, 7 November 2009 (UTC)

Yes, diffraction is the answer. See also Lens (optics) and Caustic (optics). Red Act (talk) 19:45, 7 November 2009 (UTC)

My eyeglasses work by refraction, not diffraction. -- Coneslayer (talk) 20:10, 7 November 2009 (UTC)

Note as well that even in the absence of diffraction effects your lenses aren't perfectly transparent, and they do not transmit all of the light that strikes them. Depending on the material the lenses are made from, and what coatings have been applied, somewhere in the neighbourhood of 10% of the incident light is going to be reflected or absorbed. TenOfAllTrades(talk) 19:51, 7 November 2009 (UTC)

As far as I know no corrective glasses work by diffraction but rather refraction. I'm assuming the OP has myopia as my glasses do the same thing too. If you try moving it closer or further to the surface on which the shadow projects to, you can see that the shadow changes brightness and you may notice a slight ring of light surrounding the shadow. In essence myopia corrective lenses makes parallel rays of light divergent, so that if you shine a light through it the rays now have to cover a larger area, so the area directly under the lens is darker than the surrounding. Just outside this "shadow" you can maybe see a slight halo. This is the place where it receives light from both the divergent rays from the lenses and also directly from your light source. Hyperopia corrective lenses are the opposite, they're like magnifying glasses and will form a bright spot in the centre when you try the same thing. --antilived^{T | C | G} 23:13, 7 November 2009 (UTC)

Wow, that's really bizarre that four of us used the wrong word! On a multiple choice test, I'd bet all four of us would correctly answer that lenses work by refraction, not diffraction. But somehow the wrong word stuck once it entered our heads. It's like some kind of groupthink or something. Red Act (talk) 01:32, 8 November 2009 (UTC)

Yikes! Well at least I can add "able to control brains by remote control" to my CV. DMacks (talk) 18:20, 8 November 2009 (UTC)

You could be a vampire. Vampires, and their attire/accessories, don't cast shadows when they normally would, but do cast shadows when they normally wouldn't. Can you see your reflection in a mirror? 92.230.64.60 (talk) 18:18, 8 November 2009 (UTC)

All together now: Wikipedia has an article about that. Cuddlyable3 (talk) 19:33, 9 November 2009 (UTC)

Batteries in plastic bags

If I throw multiple AAA batteries or AA batteries in plastic bags, like Ziploc bags, will a circuit, however weak, be formed by means of the plastic bag touching the ends; and will the batteries deplete faster than if I throw them in a drawer, or loose in a plastic tub, or in a paper bag? Tempshill (talk) 19:41, 7 November 2009 (UTC)

I'd say there would be no noticeable difference, since plastic is essentially an insulator. That is, unless the plastic is wet. StuRat (talk) 19:46, 7 November 2009 (UTC)

A clean dry plastic bag will not complete a circuit. There is a remote possibility that a number of batteries could arrange themselves to complete a circuit. Edison (talk) 20:15, 7 November 2009 (UTC)

Yes agreed, unless the bag is an antistatic bag used for storing electronic parts. These are usually either obviously metallic or else are slightly pink. @Edison, to form a complete loop the batteries need space enough to form something like a 3-foot circle - bigger than most plastic bags, so unlikely. In the old days the negative terminal of the battery, which is also the case, appeared as a ring around the positive terminal so it was very easy to short them out. All good quality brands now have insulated cases so this can no longer happen. SpinningSpark 21:37, 7 November 2009 (UTC)

Nine-volt batteries are also very prone to being shorted if stored loosely, due to the proximity of the terminals. Mitch Ames (talk) 01:08, 8 November 2009 (UTC)

Many small cells have a steel cylinder around them, like Duracell, perhaps painted, which could complete a circuit unless the paint is a good insulator. A 9 volt is the most likely culprit to short in a bag of batteries, agreed, or any cells in a pocket with change and keys (not the same as the OP's scenario). Edison (talk) 04:03, 8 November 2009 (UTC)

I just checked with a multi-meter, I tried a AA Duracell and a AAA Walgreens, both were good insulators except at their ends. (Even though they were both visibly shiny.) I suspect that they do it like that for specifically that reason.

Incidentally, it's not paint, it's a plastic wrapper. APL (talk) 07:25, 8 November 2009 (UTC)

Yes, plastic, at least on well known quality brands. It is possible to get through it to the metal if you have sharp meter probes but you have to push hard. For this to happen accidentally in a plastic bag would require the battery to be very severely and visibly obviously damaged. Agreed 9 volt batteries are the exception here (and other rarer types with both terminals on the same side), an unprotected pocket full of them can succeed in getting hot enough to burn your skin. SpinningSpark 09:58, 8 November 2009 (UTC)

Cylindrical cells I checked all have an insulating plastic wrapper around the steel outer casing, however shiny and metallic it looks, since otherwise it would short the + and - terminals. There is an insulating fiber washer between the - terminal and the steel surround, with the wrapper covering it. However, on Duracell 9 volt batteries, there is no plactic wrapper, just painted steel. In the 9 volt, there is an insulating fiber piece at the end between the steel case and the + and - terminals, so 9 volters are a short circuit risk even if the contact is just with the outer case. The paint layer is insulating but easily scratched through. Edison (talk) 15:48, 8 November 2009 (UTC)

I took these photos of animals for WP, but I'm not sure what they all are =(

If anyone knows who any of these guys are it would be greatly appreciated and would probably help various taxa get an image! Best regards, -Craig Pemberton (talk) 21:24, 7 November 2009 (UTC)

There are 174 pictures in there. Which ones do you want identified?! It would be a good idea to post the ones you want identified as thumbnails on this page, with numbers or tags of some sort; otherwise we may not even be talking about the same picture at any given instant. Please only post the best ones. --Dr Dima (talk) 21:45, 7 November 2009 (UTC)

Those are pretty nice, but it's clear you know what a lot of them are—you're making me kind of have to wade through them all on the off-chance I will find one of the ones you don't know and then will know what it is. You could facilitate this a little bit... (And I will disagree with Dr Dima that posting all of them is probably useful, though obviously not all will end up in articles. As a graphic designer, I have gotten a LOT of use out of high-res images on Commons that were not the "best" but were well categorized. Web space is cheap! But the blurry little beetle probably isn't worth uploading.) Your photo of the convergent evolution image should not be uploaded (the substantive content is copyrighted by the museum unless otherwise indicated—taking a new picture of a copyright image does not substantially change its copyright status). --Mr.98 (talk) 21:49, 7 November 2009 (UTC)

Okay. Should I upload some to commons, and make a gallery here? Or should I just link the most mysterious ones? Is it alright to leave the convergent evolution one on Flickr? Thanks for the feedback! -Craig Pemberton (talk) 22:07, 7 November 2009 (UTC)

As I said, you should only upload the best ones; definitely not all of them!!! Sorry if that was not clear. Look for similar pictures available in Wikimedia Commons, and only upload ones that are better than the ones already found in Commons. Do not upload any of the unsharp / unclear / partially obstructed ones. Also, if you have there a picture of critter not represented in Commons at all, you can upload that, as well. That should shorten your list from 174 to anything between 2 and 20. --Dr Dima (talk) 22:29, 7 November 2009 (UTC)

To answer your question on copyright, you will be breaching someone's copyright with the poster uploaded to Flickr (except in the unlikely event that it has a free licence). That is nothing to do with Wikipedia of course, that is between you, the museum and Flckr. sorry, I do not know what any of them are - except the first one, that's a dog. SpinningSpark 10:12, 8 November 2009 (UTC)

Rechargeable batteries

I've noticed that if the battery in my DS dies and I'm somewhere where I can't recharge it, the battery will gradually build up a charge again by itself. Why is this? --70.247.249.87 (talk) 21:51, 7 November 2009 (UTC)

Me too -- my phone will show a low battery level, then suddenly go back up. I also notice that while it's charging and the battery level is say, 70%, disconnecting the charger will make it rise to 80% -- but connecting it back again will make it drop to 70%. My hypothesis is that what is happening that less of the battery capacity becomes visible to the phone after the charger disconnecs, but this hidden capacity is later "rediscovered"? John Riemann Soong (talk) 23:21, 7 November 2009 (UTC)

There is a phenomenon in many kinds of battery called "polarization" - it has the effect of causing the battery to lose power before it's actually totally dead. Turning the thing off and letting it recover for a few seconds allow you to get a little more use out of the battery. You can see this effect in all sorts of batteries and in all sorts of situation - so it doesn't surprise me that you're seeing it in your Nintendo DS. To be 100% clear though - the battery isn't "building up a charge" - it always had that charge - it just wouldn't let you use it. It doesn't matter how long you wait beyond the first few tens of seconds, you get to use that last little bit that was in the battery - and that's it. SteveBaker (talk) 23:22, 7 November 2009 (UTC) Added link to article. Mitch Ames (talk) 01:16, 8 November 2009 (UTC)

So how is it a DS which I played out of battery has twice now managed to "build up" in excess of an hours' charge? I know I haven't charged it without remembering because I lost the charger. Vimescarrot (talk) 00:14, 8 November 2009 (UTC)

For what it's worth, I've also noticed this phenomena with my DS. If I run the battery down until it shuts itself off and refuses to turn back on, and then leave it off for a while. (Ten seconds isn't enough, but ten minutes is) I can usually get at least another half hour of play out of it. Sometimes I can do this a few times before it stops working entirely. Must be a quirk of these batteries as they age. They "die" well before they're actually "empty". APL (talk) 00:50, 8 November 2009 (UTC)

I have to leave mine for days or more to get this result. Vimescarrot (talk) 01:52, 8 November 2009 (UTC)

Note the important distinction between battery is dead and control electronics have shut down the battery. The battery's life-cycle and charge cycle will cause its voltage and current capacity to vary through its usable life; the control electronics (at the very least, an LVDO regulator) will shut the entire device down until it detects that the battery is able to operate. Sophisticated battery management circuitry may even include software to estimate the chemical lifecycle of the battery (think ACPI, though the Nintendo DS probably uses a simpler scheme); so it will make a best-guess based on current measurements and expected values. When current battery measurements do not match up to the estimated values (e.g. because of manufacturing tolerances; temperature; or poor internal modeling for the estimates) unknown behavior may result (like premature shutdowns or reporting incorrect battery levels). Chances are good that the battery has enough "juice" (current-capacity and voltage) to actually operate your device, but not enough to trigger an "all-clear" from the over-zealous power regulation circuitry. When a temperature change or just a few minutes/hours of rest for the battery's chemical boost the voltage levels back above the regulated threshold, the device works fine again. My bet is that the actual voltage level didn't change by very much - but it was hovering very close to a designed safety threshold to prevent brownout. Nimur (talk) 17:05, 8 November 2009 (UTC)

Luxon theory concerning tardyons

Does Wikipedia have any information on luxon theory, specifically on their relationship to tardyons? —Preceding unsigned comment added by Active Galactic Nuclei (talk • contribs) 22:03, 7 November 2009 (UTC)

A "luxon" is a massless particle - either a photon or a gluon. Since there are no free gluons - you might as well say skip the fancy language and say "photon" instead of "luxon". Tardyon is another neologism used (rarely) to mean anything that's moving slower than light - which is to say: Everything except photons. So you're asking whether there is information on photon theory, specifically as they relate to all normal matter? Well, yes, of course! How light and other electromagnetic radiation interacts with matter? Start with Newton - work your way forwards. SteveBaker (talk) 22:28, 7 November 2009 (UTC)

A Google search for "luxon theory" only turned up www.tardyon.de, which I guess is what prompted this question. It's a crackpot site. However, it's right when it says that "tardyons are luxons". In field theory (classical or quantum) it's useful to describe massive waves as massless waves that interact with each other in a certain way. Specifically, a wave can be divided into "left-handed" and "right-handed" parts which individually propagate at the speed of light, and the mass (if any) shows up as an interaction between those parts. In the Standard Model that interaction also involves the Higgs field, which is why the Higgs is said to "give mass" to the particles. -- BenRG (talk) 23:14, 7 November 2009 (UTC)

Here was my starting point: http://en.wikipedia.org/wiki/Massless_particle. I was hoping for anything more you might have on it? —Preceding unsigned comment added by Active Galactic Nuclei (talk • contribs) 23:46, 7 November 2009 (UTC)

I removed the reference to the "luxon theory" site. I'm not sure what to add to what I and SteveBaker already said; do you have a more specific question? -- BenRG (talk) 14:23, 8 November 2009 (UTC)

The text and link that you removed were the issue, Thank you. —Preceding unsigned comment added by Active Galactic Nuclei (talk • contribs) 18:02, 8 November 2009 (UTC)

why isn't the Wolf-Kishner reduction or the Clemmensen reduction used for meth synthesis?

Bleach (sodium hypochlorite -- failing that one could fall back to Swern oxidation) and W-K or Clemmensen would seem to do the job quite nicely. No phosphine gas? Or is red phosphorus much cheaper? (This is purely out of curiosity as I reduce an alcohol to a C-H bond for the umpteenth time on paper...) John Riemann Soong (talk) 23:39, 7 November 2009 (UTC)

Bleach has its own problems, see Bleach#Chemical interactions. My guess is that most people home-brewing their own crystal meth aren't exactly familiar with various reaction pathways that get them their product. Likely one could do it safer with the right materials. But really, these guys are just following a recipe without knowing why they do each step, and what all the process is about. --Jayron32 01:24, 8 November 2009 (UTC)

Well, couldn't the amine group be protected under acidic conditions? Or is the N-H bond that reacts? Plus even if one gets a chlorinated amine, wouldn't the chlorines be relatively easy to take off in the presence of acid, seeing how chloride a good leaving group? John Riemann Soong (talk) 01:49, 8 November 2009 (UTC)

Again, you're asking why people don't follow good organic synthesis procedures when they are brewing crystal meth in their garage. The answer is because they aren't chemists; they're gap-toothed hillbillies who didn't finish the 4th grade and are following a recipe they found on the internet. People engaged in illegal activities don't often have the time and resources to do proper, standardized experiments to work out alternate pathways. They have a recipe, they follow it, they blow up their garage when they screw up. Questioning why they don't "do it right" misses the point. It was much the same with white lightning compared to legal, regulated booze. --Jayron32 02:00, 8 November 2009 (UTC)

Well 2 questions. Does bleach oxidise alcohols under acidic conditions? How do you lyse a quartenary ammonium salt? I mean, street drug syntheses often have a fair amount of pragmatics built into them -- clearly there are clandestine chemists who cooperate with gangs or new synthesis techniques wouldn't pop up now and then. John Riemann Soong (talk) 02:06, 8 November 2009 (UTC)

Bleach-oxidation borneol→camphor using acetic acid as (co)solvent is an undergrad lab experiment. Hypochlorous acid is a stronger oxidant than hypochlorite but is less stable in solution. Exact oxidizing mechanism is a bit complicated IIRC (maybe some radical character, can't remember), but it's approximately formation and then E2-like decomposition of H-C(R₂)-O-Cl similar to Swern and Cr(VI) oxidants. But this reagent mixture sounds like a perfect way to oxidize an amine→chloramine too (that's one of the reaction types that happens in swimming pools). DMacks (talk) 14:31, 9 November 2009 (UTC)

So what would prevent you from carrying out the oxidation under acidic conditions? (Add vinegar, then sodium hypochlorite?) If the amine is R-NH2+-R I would think it couldn't quite do a nucleophilic attack on OCl-. My only worry was that the acidity would prevent the alcohol proton from leaving. John Riemann Soong (talk) 14:44, 9 November 2009 (UTC)

Some people making crystal meth are chemists. Someone has to make the recipes. In fact I would think there'd be a lot of money in finding cheaper, safer and easier ways to produce illegal drugs in your basement. Rckrone (talk) 04:48, 9 November 2009 (UTC)

How should a chemist make money by creating a cheap easy method to synthezise meth? Selling the idea on ebay or publish it as a book? The only way is to do it on his own in his basement, and that is a risk a well trained person with a good job will not take.--Stone (talk) 14:42, 9 November 2009 (UTC)

There do exist circumstances that sometimes occur in people's lives, that could cause a well-trained chemist to become desperate enough to become a meth cook. The circumstances in Breaking Bad, for example, seem fairly plausible to me. There are also psychological conditions that would make some people enjoy, or at least not fear, the risks involved with being a meth cook, to the extent that they would turn to that from a career in chemistry, even without being desperate. After all, the money is great (until you get caught or die). All it would take is an underestimation of the risks involved, which is a very common thing to do, especially among younger people. Red Act (talk) 16:20, 9 November 2009 (UTC)

energy vs frequency

The articles on frequency and energy confirm the increased frequency requires or represents increased energy but where can I find a plot of energy versus frequency for both sound and electromagnetic waves and all types of vibrations from zero frequency to Gamma and Cosmic rays? 71.100.0.254 (talk) 23:46, 7 November 2009 (UTC)

For light the formula is: E=hf, where E is energy per photon, h is Planck's constant and f is frequency. That holds for any EM radiation. Cosmic rays are just particles, they aren't usually thought of as waves (although you can get a frequency from the de Broglie wavelength if you want to, in which case the same formula will hold as for light). For sound, you can't divide it into particles, so there isn't a discrete energy. There is sound energy flux (not a great article, though...), which is the amount of energy to pass through a unit area in a unit time. --Tango (talk) 00:25, 8 November 2009 (UTC)

Actually, sound felt left out of the whole "wave-particle duality" party, so it went and got itself its own sound particle. Well, sort of. But there is a particle equivalent for vibrational energy just like there is one for electromagnetic energy. --Jayron32 01:19, 8 November 2009 (UTC)

Big "sort of"! As the first line of that article says, it only applies is a solid crystal lattice. We usually think of sound as being carried by air, since that is what we can hear, and air isn't a solid crystal lattice. --Tango (talk) 02:05, 8 November 2009 (UTC)

But what about a graph... x = frequency, y = energy? 71.100.0.254 (talk) —Preceding undated comment added 01:47, 8 November 2009 (UTC).

They're proportional, so it's a straight line, and h is positive, so it goes from bottom left to top right. --Tango (talk) 02:05, 8 November 2009 (UTC)

So then hf=mc²...? 71.100.0.254 (talk) 02:39, 8 November 2009 (UTC)

Kind of. That only works if you take m as relativistic mass. The rest mass of a photon is zero. --Tango (talk) 02:43, 8 November 2009 (UTC)

In my mind it appears I was actually thinking of a curve so I must have been thing of wavelength and not frequency. Anyway the would mean that since wavelength is inversely proportional to frequency that there must be a limit on the shortness of a wavelength (the shortest possible wavelength) to equal the greatest amount of relativistic energy for every particle? 71.100.0.254 (talk) 02:47, 8 November 2009 (UTC)

Mathematically, there is no limit to how small a wavelength can be, or therefore how much energy a photon can have. However, any wavelength shorter than a Planck length is likely to be meaningless, so the universe appears to have a practical limit built in. --Jayron32 02:53, 8 November 2009 (UTC)

Somehow I'm thinking that at that wavelength something mysterious happens like the propagation in a single direction stops and you get a stationary oscillation that is self containing otherwise known as energy in the form of mass. Sort of like a cowboy rope trick where the rope spins in a loop and then the loop moves forward and backward or some such crazy back and forth but stationary relationship like that. 71.100.0.254 (talk) 03:15, 8 November 2009 (UTC)

A single photon with wavelength equal to the Planck length would have energy equivalent to about 10^-7 kg, which is much larger than any of the particles we know of that make up matter. I don't think people really know what would happen at energy levels that high. Rckrone (talk) 07:05, 8 November 2009 (UTC)

We don't know what happens at the Planck length; we don't even know if the Planck length is special at all. If special relativity is valid (locally) then photons with Planck-length wavelengths are just like any other photons. Special relativity might be wrong, but so far there's no evidence that it is. Actually, the GLAST/Fermi project recently reported data from GRB 090510 that strongly constrains violations of special relativity at the Planck length. -- BenRG (talk) 14:09, 8 November 2009 (UTC)

It's not so much that SR could be wrong, it is that it is incomplete. SR doesn't explain the fringes we see when beaming electrons or individual photons or whatever through a double slit. We know that things happen on small scales that SR doesn't explain, the question is what actually happens at those scales and how small we need to get to see weird things. --Tango (talk) 20:14, 8 November 2009 (UTC)

By SR I really meant Lorentz invariance, which holds exactly in the Standard Model. There's no evidence (yet) that Lorentz invariance fails at any length scale. The threshold where things start to look quantum has more to do with temperature than distance. -- BenRG (talk) 01:52, 9 November 2009 (UTC)